1. Technical Field
The present invention pertain to a method and apparatus for measuring round-trip delay or travel time in a communications network while the communications network is in-service.
2. Discussion of the Prior Art
Numerous prior art communications networks send packets of information to target sites. Such networks are typically wide area networks (WAN) and include Frame Relay, ATM, SMDS, X.25 and ISDN. Long delay or travel times for packets tend to indicate an inefficient route, problems in the network, or other deficiencies which must be addressed to improve performance. Measurement of delay or travel time is conventionally accomplished by sending protocol specific packets to certain destinations capable of recognizing those packets, and then generating and transmitting a response back to the originator. The round-trip delay or travel time is measured as the absolute time from generation of the protocol specific packet to receipt of the response.
Prior art measurement of delay or travel time through communications networks suffers from major disadvantages. In particular, the measured delay or travel times include the processing delay introduced by recognition of the protocol specific packet and subsequent generation of the response. The protocol specific packets increase traffic on the network, thereby adding to the effective delay or travel time in the system. Further, delay or travel time measurements may only be made when the available protocols and equipment are capable of supporting responses to certain protocol specific packets.